Conventionally, the Latinen's model formula shown below as formula (1) is popularly employed as devolatilization performance prediction method for devolatilizing operations using a screw extruder:Ln(C0−C*)/(CL−C*)=KρSL(DdN)1/2/Q   (1),where C0 is the volatile mass concentration (ppm) at the entrance of the devolatilization region (immediately before devolatilization), CL is the volatile mass concentration (ppm) after devolatilization, C* is the gas-liquid equilibrium concentration (ppm) of volatile mass and nonvolatile mass (solution of polymer and/or rubber) under the pressure/temperature conditions for devolatilization, K is the mass transfer coefficient, ρ is the density (kg/m3) of the nonvolatile mass solution containing volatile mass, S is the boundary film surface length (m) of the nonvolatile mass solution containing volatile mass in a cross section orthogonal relative to the extruder screw flight, L is the flow path length (m) of the nonvolatile mass solution containing volatile mass in the devolatilization region, Dd is the diffusion coefficient (m2/s) of the volatile mass contained in the nonvolatile mass solution, N is the screw rotational speed (s−1) and Q is the overall processing rate (kg/s).
FIG. 16 of the accompanying drawings schematically illustrates a known twin-screw extruder, showing the configuration thereof. The above Latinen's module formula predicts the concentration of the residual volatile mass after devolatilization by way of the product of multiplication of the totalized area of the boundary film (exposed surface layer) of the nonvolatile mass containing volatile mass that is updated by revolutions of the screw in the devolatilization region of the twin-screw extruder as shown in FIG. 16 and the diffusion rate of volatile mass from the nonvolatile mass, or the ratio of the weight of the nonvolatile mass containing devolatilized volatile mass to the weight of the nonvolatile mass containing the entire volatile mass.
In FIG. 16, 100 denotes a barrel that can be heated and cooled, 200 and 300 respectively denote a screw and a vent (an aperture for removing the isolated volatile mass) and 401 and 402 denote respective kneading screws, while 501 and 502 denote parts totally filled with nonvolatile mass containing volatile mass in the barrel and 600 denotes a part (devolatilization region) that is not totally filled with nonvolatile mass containing volatile mass and hence nonvolatile mass is flowing.
In the Latinen's model formula, each of C0, C*, CL, ρ and Dd represents a characteristic factor of a nonvolatile mass, a volatile mass or a nonvolatile mass solution containing volatile mass and N and Q represent operation factors of an extruder. These factors can vary according to the environment and conditions of devolatilization operation.
“SL(DdN)1/2” in the Latinen's model formula can be substituted by “SL(Dd/(1/N))1/2” and regarded as the exposed surface layer of the nonvolatile mass solution containing volatile mass that is formed in the barrel and the screw per unit time.